In order to study the effect of molybdenum ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by molybdenum ions in the fluence range 1 x 10(16) to 5 x 10(17) ions cm(-2) at maximum 160degreesC, and at an extracted voltage of 40kV. The valence of the surface layer was analyzed by X-ray photoemission spectroscopy. Three-sweep potentiodynamic polarization measurements were employed to value the aqueous corrosion resistance of zirconium in a 1N H2SO4 solution. Scanning electron microscopy (SEM) was performed for the three-sweep potentiodynamic polarized samples. It was found that the aqueous corrosion resistance of zirconium implanted with molybdenum declined with raising fluence. The greater is the implantation fluence, the bigger is the decline. And the natural corrosion potential of the implanted zirconium became more positive than that of the as-received zirconium. Finally, the mechanism of the corrosion resistance decline of the molybdenum-implanted zirconium is discussed. (C) 2004 Elsevier B.V. All rights reserved.